Turbine rotor



9, 1939. E. KLIEMANN 2,357,827

' TURBINE ROTOR I Filed Feb. 24} 1958 Inventor: Erich Kliemann,

y 7, His Attorney.

Patented May 9, 1939 mm QFFiCE TURBINE ROTOR,

Erich Kliemann, Berlin, Germany, assignor to General Electric Company, a corporation of New York Application February 24, 1938, Serial No. 122,372

- 1 In Germany May 12, 1937 3 Claims.

The present invention relates'to bucket wheels such as are used in elastic fluid turbines for transforming thermo-dynamic energy of steam or like elastic fluid into mechanical energy. The invention relates morespecifically to the kind of bucket wheels which comprise a disc element and a row or rows of buckets secured to the disc element by a dovetailed connection between a base portion of each bucket and the rim of the disc.

In the usual arrangement of this kind, shoulder portions of the dovetail forming rim portions are cut away defining a notch opening through which the buckets are inserted and slid along the rim during assembly. Difficulties are experienced in closing these notch openings by means of a notch opening bucket, a notch opening block, or other means, to prevent relative movement of the buckets on the .rim, and to lock them securely in place. In modern high speed service where the buckets are subjected to considerable centrifugal forces, it is no longer desirable to insert a bucket in the notch opening because of the great centrifugal forces and, in many cases, it is not even desirable to put into the notch opening a heavy block or filler.

It is an object of the present invention to provide an improved construction and arrangement of bucket wheels of the type above referred to whereby the buckets are rigidly secured to the rim of the disc and prevented from relative movement thereon.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and claims appended thereto in connection with the accompanying drawing.

In the drawing, Fig. 1 illustrates an exploded, perspective View of a bucket wheel portion embodying my invention, and Fig. 2 is a side view of the assembled bucket wheel with the special locking means in position.

The arrangement shown in Figs. 1 and 2 comprises a disc member ID having a grooved rim portion defining a dovetail The dovetail of the rim forms shoulders |2 and I3 which are partly cut away to form a notch opening l4. Buckets l5 comprising blades l6 and base portions H, which latter define inverted dovetails, are inserted through the notch opening and slid to the left or right along the rim of the wheel.

In accordance with my invention I provide a locking screw l8 having a threaded portion l9 and a conically-shaped head 20, the taper of the sides thereof corresponding with the radius of curvature of the disc.

The head 20 may be provided with a slot by means of which a tool may be applied to the screw to force it into the hole provided in the rim of the disc. However, due to the length of th adjacent buckets and the narrow clearance between them, a screw driving tool cannot be properly used for this purpose. Accordingly, I prefer to use a screw having a shaft 2| extending axially from the top of the head and integral therewith. This shaft is of a length greater than that of the blades so that the upper end thereof extends beyond the ends of the buckets when the screw is in place in the disc as shown in dotted line in Fig. 2.

The enlarged upper end 22 or head of the shaft is slotted or otherwise adapted for the application of a suitable tool used to fasten the locking screw in position. The lower end of the shaft 2| adjacent the head 20 is provided with an annular notch 23 forming a weakened section to facilitate the separation of the shaft from the screw as will be described hereinafter.

In the periphery or rim of the disc and cen- A trally positioned therein with respect to the notched portion I l, a hole 24 is bored and threaded for the reception of the threaded portion l9 of the locking screw I8. During assembly, the buckets with their bases are slid along the rim of the disc, and. after all of the buckets have thus been assembled on the disc, the looking screw I8 is inserted into the hole 24. As the member I8 is screwed into the disc, the tapered sides of the screw head are adapted to engage with the bases of the adjacent buckets which accordingly are wedged apart with a pressure exerted circumferentially with respect to the disc I0 and firmly secured thereto. The facing bases of the buckets adjacent the locking screw may be recessed as shown at 25 to provide an enlarged contact surface for the screw head. With the locking screw I8 driven to its lowermost position, the shaft 2| may be removed from the screw head 28 by applying an additional torque to the headof the shaft 2|. Due to the notch 23 at the lower end of the shaft providing a weakened section, the additional torque will cause the shaft 2| to shear from the head 20. The shear strength of the weakened shaft section is less than the shear strength of the threaded section 9 so that the screw head 2|) will not be twisted off during the'driving operation. As pointed out above, the locking screw I8 prevents the row of buckets,

considered as a unit, from moving on the rim of the disc and securely locks them. in position.

If it is later desired to exchange any of the blades on the disc, the threaded screw is removed from the disc by boring and a new one is substituted for it after the new blades have been inserted.

Having described my invention together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A bucket wheel comprising a disc member having a rim and a row of buckets having bases secured to the rim by a dovetail connection therebetween, the rim having a notch opening through which the bucket bases are inserted during assembly, a screw threaded into the periphery of the rim. at the notch opening, said screw provided with a conical head the taper of which corresponds with the radius of curvature of the wheel adapted to engage with and exert a circumferential pressure against the bases of the adjacent buckets, recesses in the bases of adjacent buckets for cooperation with and providing enlarged seating surfaces for said screw head whereby relative movement between the disc member and the buckets is prevented.

2. A bucket wheel comprising a disk member having a rim and a row of buckets having bases secured to said rim by a dovetail connection therebetween, the rim having a notch opening through which said bucket bases are inserted during assembly, a screw threaded into the periphery of the rim at the notch opening between adjacent buckets, said screw provided with means adapted to engage with and exert a circumferential pressure against the bases of the buckets on either side thereof to prevent relative movement between the disc member and the buckets.

3. A bucket wheel comprising a disc member having a rim and a row of buckets having bases forming a dovetail connection with the rim, a portion of the rim being cut away to form a notch opening through which the buckets may be inserted during assembly, a screw threaded into the periphery of the rim at the notch opening, said screw having a head adapted to engage with and exert a pressure circumferentially with respect to said disc against the bases of the adjacent buckets as said screw is driven into said rim. to prevent relative circumferential movements between said disc member and said buckets.

ERICH KLIEMANN. 

